General purpose speed sensor with military-type socket .
C & A magnetic pickups convert mechanical motion to an ac voltage without mechanical linkage. These permanent magnet transducers have an external magnetic field which when altered by a moving ferrous object, generates an ac voltage in a coil wound over the magnet. This ac voltage has a frequency directly proportional to RPM when the pickup is mounted in proximity to the teeth of a rotating gear. The magnitude of the voltage is proportional to the rate of charge of magnetic flux, therefore the voltage is proportional to the magnetic flux, therefore the voltage is proportional to speed.